Games bosses were braced for a typhoon tonight as athletes struggled in blistering heat.
Forecasters warned tropical storm ‘Nepartak’ was sweeping through the Philippine Sea south of Japan at speeds of up to 40mph.
It could disrupt the men’s triathlon on Monday where Team GB’s Rio silver medallist Jonny Brownlee is hoping to go one better.
The tropical ‘depression’ was predicted to move north before taking a sharp turn west towards the mainland.
Meteorologists at AccuWeather were hopeful Nepartak will stay at tropical storm level, but risks remain it could escalate into a typhoon as it hits the Japanese mainland, which is the same strength as a hurricane.
Competitors faced fierce heat and humidity in the first full day of events today.
Organisers adapted air conditioning units with makeshift plastic air ducts for the tennis where Andy Murray and Joe Salisbury beat a French pairing in the doubles.
Murray, 34, said: “It is hot but it didn’t feel too bad on the court. We have these things blowing out cold air and the end changes help a lot.
“We did some prep in the heat before coming out. The conditions are fairly lively, it is not hard to control the ball but you get a little bit more pace on the serve.”
Cyclists in the men’s road race shoved ice into their jerseys passed to them by support staff on the roadside.
Some athletes used Bluetooth pills that are swallowed so coaches can monitor body temperature.
Team GB’s specialists had examined ways of keeping competitors cool during the Games before they arrived.
Boss Mark England said they had worked hard on “heat mitigation” measures.
He added: “We have a big medical team here, there’s a great level of support. Everybody is in great spirits and great physical form.”
Japan’s weather bureau issued heatstroke alerts for five consecutive days last week as temperatures in Tokyo reached 33.1C
The capital is one of the hottest cities on earth in the summer due to its latitude.
Local Misuzu Ueno, 24, said: “The Japanese summer is abnormal. There’s humidity and the heat is ridiculous – this climate is not suitable for the Olympics.”
Hundreds died due to the heat of Japan’s summers of 2018 and 2019 and tens of thousands were hospitalised.